Systems and devices useful for performing endo-surgery are known. A number of devices have been developed for use in minimally invasive surgical procedures, including orthopedic and podiatric soft tissue surgeries such as nerve and tendon release procedures. In particular, certain devices have been developed for performing “carpal tunnel” surgery to relieve the symptoms of “carpal tunnel syndrome”, in which the flexor retinaculum or “transverse carpal ligament” (TCL) is severed.
Carpal tunnel syndrome refers to numerous clinical signs and symptoms resulting from pressure on the median nerve inside the carpal tunnel. Splints that immobilize the wrist in a neutral position are the most commonly used nonsurgical treatment for carpal tunnel syndrome because an unbent wrist maximizes the size of the carpal tunnel, which reduces pressure on the median nerve. Physical therapy and special hand exercises are also used to relieve mild to moderate symptoms of carpal tunnel syndrome. However, when the symptoms persist or become intolerable, surgical decompression of the nerve by release of the transverse carpal ligament, or flexor retinaculum, is performed.
In early techniques, open carpal tunnel release surgery (OCTR) was performed to relieve carpal tunnel syndrome.
OCTR is typically performed under local anesthesia, where a longitudinal incision is made in the base of the palm and sometimes extending into the wrist. This incision opens the skin, subcutaneous fat, palmar fascia and palmaris brevis muscle to expose the transverse carpal ligament, which is cut with a surgical blade. The cut ligament springs open and immediately provides more space for the median nerve to pass through the carpal tunnel. The incision is then closed with sutures.
Although OCTR is currently the most commonly performed surgical carpal tunnel release procedure, it can lead to postoperative pain and morbidity lasting up to six months.
Recent advances involve endoscopic carpal tunnel release surgery (ECTR), which is performed as a single-portal technique or a double-portal technique. For a single-portal technique, one incision is made either in the palm or in the forearm proximal to the wrist. For a double-portal technique, two incisions are made, one in the palm and one in the forearm proximal to the wrist.
In 1987, the first reports of endoscope use in carpal tunnel release surgery were provided by Okutsu, a Japanese orthopedist. In Okutsu's technique, an incision is made 3 cm proximal to the distal wrist crease. Then, a clear plastic cannula is inserted into the carpal tunnel with an endoscope inside; under direct visualization, the transverse carpal ligament (TCL) is divided distally to proximally, with a hook knife.
The next development occurred in the early 1990's with John Agee and Francis King, who created a single-portal endoscopic carpal tunnel release system having a probe with a trigger-activated mechanism for engaging a blade to cut the TCL. The Agee technique involves activating the trigger mechanism to engage the blade and elevating it perpendicularly above the upper surface of the probe. The instrument is then withdrawn, and under direct visualization, the TCL is divided in a distal to proximal direction. The Agee systems and techniques are disclosed in Agee, et al. U.S. Pat. No. 4,962,770; U.S. Pat. No. 4,963,147; U.S. Pat. No. 5,089,000; U.S. Pat. No. 5,306,284; and U.S. Pat. No. 5,613,976.
Jay Menon created another single-portal technique involving a cannula with a D-shaped cross-section and an obturator. In Menon's technique, dilators are inserted through the antebrachial fascia into the carpal tunnel. Then, a cannula is passed under the TCL and a forward knife is used to cut the ligament proximally to distally while visualizing the TCL with an endoscope immediately following the knife.
Ather Mirza created yet another single-portal technique involving a cannula, a scope mounted cutting blade and a tapered obturator. The Mirza technique involves inserting an elongate insertion member through the cannula and introducing the combined cannula and insertion member under the TCL. Then, after advancing the obturator beneath the TCL, the scope mounted cutting blade is inserted through the cannula to operatively engage the tissue. Mirza's systems and techniques are disclosed in Mirza U.S. Pat. No. 5,366,465; U.S. Pat. No. 5,578,051; U.S. Pat. No. 5,968,061; and U.S. Pat. No. 7,041,115.
The first reports of double-portal ECTR were provided by James Chow in 1989, who developed a slotted cannula and obturator, synovial elevator, probes, and a series of knives for use in his technique. The Chow system is disclosed in U.S. Pat. No. 5,029,573. Then, in 1992, Michael Brown introduced an improved double-portal technique, where a slotted cannula is inserted in the carpal tunnel under the TCL and a surgeon's dominant hand is used to cut the ligament distally to proximally. The Brown system is disclosed in U.S. Pat. No. 5,323,765.
The ECTR procedures described above significantly reduced the postoperative pain, morbidity and recovery time associated with OCTR procedures.
However, there is a continuing need to improve ECTR and provide simple, workable systems and techniques that better protect the nerves and other portions of the hand during surgery. What is further needed is an improved, less cumbersome endo-surgical system that can be adapted for use with many other types of delicate endo-surgery, and not just for ECTR.
In the past, the performance of a minimally invasive surgical procedure, such as ECTR, has often required the use of a plurality of instruments for performing the procedure. For example, prior art surgical procedures often required the use of one or more dissectors, dilators, obturators, elevators or rasps to separate tissue and create a space for the visualization/cutting cannula, prior to its insertion and advancement in the body. Additionally, the visualization/cutting cannulas used in such prior art procedures, do not have any way to adequately inhibit nerves, tendons and other tissue from invading the surgical space defined by the cannula, as the same is advanced. As a result, these devices have an increased risk of severing unintended tissue
The particular shape of the prior art cannulas can have an impact on the particular procedure being performed. For example, certain prior art cannulas having a uniform cross-section or a taper (i.e., a reducing width) towards the distal end, do not provide the surgeon with tactile feedback indicating when the carpal tunnel has been traversed and the distal edge of the TCL has been reached. Additionally, some prior art cannulas tend to be somewhat narrow relative to the width of the carpal tunnel. This narrowness allows significant displacement of the cannula relative to the center line of the TCL, thus increasing the risk of coming into contact with, or even severing, tissues which the surgeon does not intend to cut. For example, FIG. 15 shows a narrow, prior art cannula that has displaced within the carpal tunnel, such that its knife is potentially endangering the ulnar nerve and/or artery.
Further, cannulas exist having a circular, “D” or “U” shaped cross section, that permit rotation of the cannula around its longitudinal axis. However, when a blade or knife is deployed in connection with such a cannula, any inadvertent rotation of the cannula further increases the risk of severing tissues which the surgeon does not intend to cut. For example, FIG. 16 shows a prior art cannula that has inadvertently rotated such that its knife is potentially endangering the ulnar nerve and/or artery.
Additionally, certain cannulas used for endo-surgical procedures, such as a carpal tunnel release procedure, have been provided with a flat upper surface at the distal end, continuous with the upper surface of the cannula shaft. This flat upper surface does not adequately displace the fat pad that lies beyond the distal edge of the TCL, thus making it difficult for the surgeon to visualize the location where division of the TCL should begin.
Further, prior-art devices possess blades that are deployed by articulating into an inclined position and that decline to a closed position. This trajectory can cause loose tissue to be pinched between the blade and certain other features of the cannula. The pinched tissue may then prevent the blade from being fully closed, leaving it partially exposed in an unsafe position.
What is needed is a cannula for an endo-surgical procedure wherein the shape of the cannula has been optimized to aid the surgeon in cutting only those tissues that the surgeon intends to cut. What is additionally needed is a cannula, the shape of which provides the surgeon with useful tactile feedback while performing a minimally invasive endo-surgical procedure. What is further needed is a cannula that encompasses various surgical steps, and thereby eliminates the need for a plurality of tools, be it for separating tissue, clearing a surgical space prior to insertion of the cannula, or otherwise.